Insecticidal composition

ABSTRACT

The presence of isobornyl thiocyanoethyl ether exerts a synergistic effect on the insecticidal activity against harmful wood eating insects of certain known insecticides selected from the group consisting of imidacloprid, phenyl pyrazole insecticides, pyrethroid insecticides and non-ester pyrethroid insecticides.

BACKGROUND OF THE INVENTION

The present invention relates to a novel insecticidal composition forthe eradication of harmful wood eating insects and comprising a knowninsecticide in admixture with isobornyl thiocyanoethyl ether (referredto herein as "IBTE").

Wood eating insects, such as termites, powderpost beetles (Lyctidae),lesser grain borers (Bostrichidae), drugstore beetles (Anobiidae), andlonghorn beetles (Cerambycidae), cause considerable economic loss inmany parts of the world. Although many different compounds have beenproposed for use in their eradication, none has found completeacceptance for various reasons.

Traditionally, the active ingredient used for exterminating harmful woodeating insects such as those referred to above has been an inorganiccompound (such as arsenic, arsenic pentoxide, arsenic trioxide, sodiumhydrogen arsenate, chrome oxide, potassium dichromate, sodiumdichromate, copper carbonate hydroxide, copper chloride, copper sulfate,sodium fluoride, ammonium fluoride, sodium silicofluoride, sodiumborofluoride, boric acid or borax) or an organochlorine compound, suchas chloronaphthalene, DDT, BHC, linden, dieldrin or chlordane. Thesecompounds are frequently used because of their excellent stability andresidual effect in wood and their low cost.

However, these compounds are highly toxic, and organochlorine compounds,in particular, are stable in the environment, for example in the soil.They are also very persistent in the human and animal body, and so, oncethey have entered the food chain, for example in the fat in fish orshellfish, they remain in the ecosystem, where their presence has becomea problem. The manufacture, sale, import, and the like of thesecompounds are restricted in many countries, and most of them areprohibited from being used.

In place of these compounds, organophosphorus compounds, such aschlorpyrifos, pyridaphenethion, phoxim, fenitrothion, and chlorvinphos,and carbamate compounds, such as propoxur, fenobcarb, and carbaryl, havebeen used as agents for exterminating harmful wood eating insects.

However, organophosphorus compounds and carbamate compounds have thedisadvantages that they have unpleasant odors, and that they are highlytoxic, unstable to alkalis, unstable to soil bacteria and unstable tosunlight. Moreover, they must be used at a relatively high concentration(1% or more). Microcapsulation and similar procedures have beenattempted to overcome these disadvantages, but this results in theproblem of higher cost.

Recently, pyrethroid compounds, such as allethrin or permethrin,pyrethroid-like compounds, such as etofenprox. or silafluofen, andnicotinic acid compounds bound to nitroimidazolidylidene amine, such asimidacloprid, which have a chemical structure completely different fromthose of the forgoing compounds, have been used as agents forexterminating harmful wood eating insects. These pyrethroid compounds,pyrethroid-like compounds and imidacloprid are highly effective but havethe disadvantage of high cost.

Japanese Patent Application Laid-Open No. Hei-7-69819 discloses the useof isobornyl thiocyanoalkyl ethers, including IBTE, for exterminatinghouse dust mites, such as Acaridaes. Further, Japanese PatentApplication Laid-Open No. Sho-46-34420 discloses that IBTE has aninsecticidal effect on harmful insects such as flies, mosquitoes andcockroaches. However, IBTE is not been known to be effective forexterminating harmful wood eating insects such as termites. Indeed, asis shown hereafter, by itself, it has very little effect on suchinsects.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to develop an insecticidalcomposition which is preferably both inexpensive and has a powerfulinsecticidal activity against harmful wood eating insects, such astermites, which can cause severe damage to buildings.

We have now surprisingly found that a composition comprising a mixtureof various known insecticidal compounds with IBTE exhibits a synergisticeffect. Thus, it is possible to achieve a high insecticidal effect,whilst using far lower amounts of the expensive insecticides incombination with the inexpensive IBTE, which, by itself, exhibits nosuch activity against harmful wood eating insects.

Thus, the present invention provides an insecticidal composition havinginsecticidal activity against harmful wood eating insects and comprisingeffective amounts of at least one of the known insecticides listed belowin combination with IBTE.

DETAILED DESCRIPTION OF INVENTION

Isobornyl thiocyanoethyl ether (IBTE), which is used in the presentinvention may be represented by the following formula (I): ##STR1## Thiscompound is known to be effective against harmful insects, such as houseflies, cattle flies, mosquitoes, fleas, lice, ants, moths, cockroaches,and bedbugs, and against mites, such as the Acaridae, and house dustmites.

The known insecticides used in the present invention are selected fromthe group consisting of imidacloprid, phenyl pyrazole insecticides,pyrethroid insecticides and non-ester pyrethroid insecticides.

Imidacloprid, which has the IUPAC name1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylidene amine, may berepresented by the following formula (II): ##STR2## This compound isknown to demonstrate a strong insecticidal activity at a low dosageagainst harmful insects of the order Hemiptera (e.g. plant hoppers, leafhoppers and aphids), harmful insects of the order Coleoptera (e.g. riceleaf beetles and weevils), harmful insects of the order Thysanoptera(e.g. thrips) and on some harmful insects of the order Lepidoptera. Itis, accordingly, registered and used as an insecticide for the treatmentof rice in paddy fields, as well as for vegetables, fruit trees, and thelike. Recently, imidacloprid has been further proposed for use as anagent for exterminating harmful wood eating insects because it has anexcellent and powerful insecticidal activity against such insects.

An example of a phenyl pyrazole insecticide is fipronil, which has theIUPAC name(±)-5-amino-1-(2,6-dichloro-α,α,α-trifluoro-p-tolyl)-4-trifluoromethylsulfinylpyrazole-3-carbonitrile,and which may be represented by the following formula (III): ##STR3##This compound, which is very expensive, is used primarily as anacaricide, and has not been used for the control of harmful wood eatinginsects.

Pyrethroid compounds that can be used in the present invention arecompounds having a cyclopropane carboxy group. Examples of pyrethroidinsecticides include allethrin, permethrin, cypermethrin, phenothrin,cyphenothrin, fenpropathrin, deltamethrin, tralomethrin and fenvalerate.These insecticide compounds are effective for exterminating sanitaryinsect pests and/or agriculturally harmful insects. They arestructurally modified by synthetic chemistry from naturally occurringpyrethrins, which are present in pyrethrum flowers.

Preferred pyrethroid insecticides include allethrin and permethrin.

Allethrin has the IUPAC name (RS)-3-allyl-2-methyl-4-oxocyclopent-2-enyl(1RS,3RS;1RS,3SR)-2,2-dimethyl-3-(2-methylprop-1-enyl)cyclopropanecarboxylateand may be represented by the following formula (IV): ##STR4##

Permethrin has the IUPAC name3-phenoxybenzyl(1RS,3RS;1RS,3RS)-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylateand may be represented by the following formula (V): ##STR5##

The non-ester pyrethroids are pyrethroid-like compounds which aresimilar to pyrethroid compounds. These compounds are free of acyclopropane carboxy group, and examples of such compounds includeetofenprox and silafluofen. These insecticidal compounds are effectivefor exterminating sanitary insect pest and/or agriculturally harmfulinsects. They, too, may be prepared by structural modification bysynthetic chemistry of naturally occurring pyrethrins which are presentin pyrethrum flowers.

Preferred non-ester pyrethroid insecticides include etofenprox andsilafluofen.

Silafluofen has the IUPAC name (4-ethoxyphenyl)3-(4-fluoro-3-phenoxyphenyl)propyl!(dimethyl)silane and may berepresented by the following formula (VI): ##STR6##

Etofenprox has the IUPAC name 2-(4-ethoxyphenyl)-2-methylpropyl3-phenoxybenzyl ether and may be represented by the following formula(VII): ##STR7##

Of the insecticides listed above, we prefer imidacloprid, allethrin,etofenprox, or silafluofen, more preferably, imidacloprid andpyrethroid-like compounds, most preferably imidacloprid or etofenprox.

We have surprisingly found that, when IBTE and one or more of theseknown insecticides are used together in suitable amounts, the resultingcombination has a higher insecticidal activity against harmful woodeating insects and a higher inhibitory activity to prevent termites frommaking pores in soil, at a lower concentration than when eithercomponent was used alone, that is, we have found an excellentsynergistic effect.

The ratio of IBTE to the above insecticide in the composition of thepresent invention is preferably in the range of from 1:1 to 10:1, morepreferably from 3:1 to 5:1, and most preferably about 5:1. In the caseof a mixture of IBTE and imidacloprid, a preferred ratio may be from 1:1to 9:1. The composition of the present invention may be used in variousforms as necessary. For example, it may be used as oil solution, anemulsion, a wettable powder, a flowable composition, a microcapsulesuspension, a powder, granules, or a coating agent. A suitable adjuvant(such as a solvent, an emulsifying agent, or a dispersant) may, ifdesired, be included for use in this case.

Further, the insecticidal composition of the present invention can beused in combination (by blending) with such organic iodine type agentsas IF-1000, sanplas, troysanpolyphase, and the like; triazole typeagents such as azaconazole, propiconazole, tebuconazole, cyproconazole,and the like; or antiseptic antifungal agents such as thiabendazole,dichlofluanid, xylazane-A1, xylazane-B, and the like so as to improveits efficacy.

The concentration of the active component in the composition of thepresent invention in practical use is preferably in the range of from0.05 to 1.5% by weight as (IBTE+the insecticidal compound).

The invention is further illustrated by the following non-limitingExamples, which show compositions of the present invention and theefficacy of the combination of active compounds of the presentinvention.

EXAMPLE 1

A solution of each of the following insecticides, either alone or incombination with IBTE in the specified proportion by weight, in acetonewas applied to Formosan subterranean termites in a predetermined amountper termite, and the mortality rate of the termites was examined after24 hours at 26±1° C.

In each case, 2 groups were used with each treatment group having 10termites.

The results are shown in Table 1.

                  TABLE 1    ______________________________________    Insecticide   Mortality rate of termites (%)    Amount        Weight ratio of insecticide:IBTE*.sup.1    Name    (10.sup.-3 μg)                      0:0   0:1  1:0  1:1   1:3  1:5    ______________________________________    Imidacloprid            0.28                 50   65    80    90            0.40                 50   80    90   100            0.56                 80   90    100  100    Allethrin            20.0                 30   55    80    90            30.0                 55   90    95   100            40.0                 75   95    100  100    Etofenprox            5.0                  15   80    90    95            7.0                  10   100   100  100            10.0                 45   100   100  100    Silafluofen            5.0                   0   45    90   100            7.0                  50   80    100  100            9.0                  90   100   100  100    IBTE alone            150.0           0    Control           0    ______________________________________     *.sup.1 The ratio is relative to the amount of insecticide. Thus, for     example, where the amount of imidacloprid is 0.28 × 10.sup.-3 μg     and the ratio is 1:1, the amount of IBTE is also 0.28 × 10.sup.-3     μg.

EXAMPLE 2

A solution of each of the following insecticides, either alone or incombination with IBTE in the specified proportion by weight, in acetonewas applied to previously air-dried soil, and then the soil wasair-dried and mixed sufficiently so that the soil contained theinsecticide or mixture at a predetermined concentration per unit weight.A 5 cm layer of the soil was then placed into a glass tube of about 1.5cm inner diameter, and distilled water was added thereto, to adjust thedegree of water saturation in the soil to about 50%. This glass tube wasconnected at one end to a vessel containing 40 worker termites and atthe other end to a vessel containing wet wood powder. It was left for 4days at 26±1° C. in the dark and the degree to which the termites wereinhibited from penetrating through the soil was examined. Eachexperiment was carried out in duplicate.

The results are shown in Table 2.

The criteria for evaluating the degree of inhibition are as follows:

+: The termites were inhibited from penetrating in both test groups.

±: The termites were inhibited from penetrating in only 1 group.

-: The termites were not inhibited from penetrating in either group.

                  TABLE 2    ______________________________________                    Degree of inhibition of pore making    Insecticide     Mixing ratio of    Concentration   test insecticide compound:IBTE*.sup.1    Name    in soil(ppm)                        0:0    0:1  1:0  1:1  1:3  1:5    ______________________________________    Imidacloprid            30.0                    +    +    +    +            15.0                    -    +    +    +    Etofenprox            80.0                    +    +    +    +            40.0                    -    +    +    +    Permethrin            80.0                    +    +    +    +            40.0                    -    -    +    +    IBTE    200.0              -    Cont.   0           -    ______________________________________

EXAMPLE 3

Wood was surface treated with a 100 ml/m² solution of each insecticide,either alone or in combination with IBTE in the specified proportion byweight. It was then air-dried and used as a test sample. This testsample and 10 insects of powderpost beetle (Lyctidae) were introducedinto a beaker which was then left in a thermostatic chamber at 25° C.under 70% humidity for a predetermined period. After the insects hadlaid eggs on the test sample, the insects were removed. The number ofinsects hatched from the eggs on each test sample were counted. 3 groups(Group 1, Group 2 and Group 3 in the following Table) were used for eachtest. The results are shown in Table 3.

                  TABLE 3    ______________________________________    Insecticide           Concentration for                     Number of Hatched Insects    Name     Treatment(%)                         Group 1 Group 2                                       Group 3                                             Average    ______________________________________    Imidacloprid             0.02        3       6     4     4             0.04        1       0     0     0    Imidacloprid +             0.02 + 0.02 1       2     2     2    IBTE     0.02 + 0.06 0       0     0     0             0.02 + 0.10 0       0     0     0    Allethrin             0.05        8       7     8     8             0.10        2       2     3     3    Allethrin +             0.05 + 0.05 5       3     4     4    IBTE     0.05 + 0.15 2       2     1     2             0.05 + 0.25 0       0     0     0    Permethrin             0.04        6       4     7     6             0.08        1       0     0     0    Permethrin +             0.04 + 0.04 5       5     3     4    IBTE     0.04 + 0.12 3       3     1     2             0.04 + 0.20 0       0     0     0    Etofenprox             0.04        3       4     3     3             0.08        0       0     0     0    Etofenprox +             0.04 + 0.04 1       1     2     1    IBTE     0.04 + 0.12 2       0     1     1             0.04 + 0.20 0       0     1     0    Silafluofen              0.025      7       8     5     7             0.05        2       0     3     2    Silafluofen +             0.025 + 0.025                         4       4     5     4    IBTE     0.025 + 0.075                         1       0     1     1             0.025 + 0.125                         0       0     0     0    IBTE     0.75        12      10    11    11             1.5         2       1     1     1    Cont.    0 + 0       13      16    15    15    ______________________________________

EXAMPLE 4

A filter paper treated with an acetone solution containing one of thefollowing insecticides, either alone or in combination with IBTE in thespecified proportion by weight, at the concentration specified in thefollowing Table was air-dried. Each filter paper was placed into a testtube, and 10 worker termites were released into each test tube. The testtubes were then placed in a room at 26±1° C. After 4 days, thepercentage kill was assessed for each treatment group. The experimentwas carried out in duplicate for each compound or mixture. The resultsare shown in Table 4.

                  TABLE 4    ______________________________________    Insecticide    Mortality rate of termites (%)    Concentration  Weight ratio of insecticide:IBTE*.sup.1    Name    (ppm)      0:0    0:1 1:0  1:1  1:3  1:5    ______________________________________    Fipronil             14                   65   100  100  100             10                   50   100  100  100             7                    15    70  100  100             5                    10    70   90  100    Etofenprox            200                   75   100  100            100                    5    70   90  100    Silafluofen            150                   45    65  100             75                   15    35   60   85    Allethrin            100                    5    40  100    IBTE alone            3000              0    Control            0    ______________________________________

The above results demonstrate that the presence of IBTE, which, alone,has no effect on termites or similar harmful wood-eating insects,results in a real synergistic effect.

We claim:
 1. An insecticidal composition having insecticidal activityagainst harmful wood-eating insects, comprising synergistic effectiveamounts of (i) at least one insecticide selected from the groupconsisting of etofenprox and silafluofen in combination with (ii)isobornyl thiocyanoethyl ether.
 2. The composition of claim 1, whereinsaid insecticide is etofenprox.
 3. The composition of claim 1, whereinsaid insecticide is silafluofen.
 4. The composition of claim 1, whereinthe weight ratio of said isobornyl thiocyanoethyl ether to saidinsecticide is from 1:1 to 10:1.
 5. The composition of claim 1, whereinthe weight ratio of said isobornyl thiocyanoethyl ether to saidinsecticide is from 3:1 to 5:1.
 6. The composition of claim 1, whereinthe weight ratio of said isobornyl thiocyanoethyl ether to saidinsecticide is about 5:1.
 7. The composition of claim 2, wherein theweight ratio of said isobornyl thiocyanoethyl ether to said insecticideis about 5:1.
 8. The composition of claim 3, wherein the weight ratio ofsaid isobornyl thiocyanoethyl ether to said insecticide is about 5:1. 9.The composition of claim 1, which further comprises an effective amountof an organic iodine insecticide, a triazole insecticide, or anantiseptic antifungal insecticide.
 10. The composition of claim 1, whichfurther comprises an effective amount IF-1000, sanplas,troysanpolyphase, azaconazole, propiconazole, tebuconazole,cyproconazole, thiabendazole, dichlofluanid, xylazane-A1 or xylazane-B.11. A method of eradicating harmful wood-eating insects by applying tothe wood-eating insects or to soil or wood a composition comprisingsynergistic effective amounts of (i) at least one insecticide selectedfrom the group consisting of etofenprox and silafluofen, in combinationwith (ii) isobornyl thiocyanoethyl ethyl.
 12. The method of claim 11,wherein the insecticide is etofenprox.
 13. The method of claim 11,wherein said insecticide is silafluofen.
 14. The method of claim 11,wherein the weight ratio of said isobornyl thiocyanoethyl ether to saidinsecticide is 1:1 to 10:1.
 15. The method of claim 11, wherein theweight ratio of said isobornyl thiocyanoethyl ether to said insecticideis 1:1 to 9:1.
 16. The method of claim 11, wherein the weight ratio ofsaid isobornyl thiocyanoethyl ether to said insecticide is 3:1 to 5:1.17. The method of claim 11, wherein the wood-eating insects are selectedfrom the group consisting of termites and powderpost beetles.